Circuit breaker



'Patented oci. 31, 1939 PATENT oFFlcE CIRCUIT BREAKER John G. Jackson,Detroit, Mich.,v assigner to Square D Company, Detroit, Mich., acorporationof Michigan Application July 25, 193s, serial No. 92,644

13 Claims.

This invention relates to devices for making and breaking electriccircuits and more particularly to electric circuit breakersautomatically operable in response to current overload.

One object of the present invention is to provide an improved circuitbreaker` assembly adapted for main and branch circuit protection.

Another object of the invention is the provision of an electric circuitbreaker having a main circuit breaker mechanism capable of ,interruptingshort circuit currents and branch circuit breaker mechanisms for theindividual branches capable of independently opening their respectivebranch circuits on the occurrence of moderate overloads.

Another object of the invention is the provision of an electric circuitbreaker having a main circuit breaker mechanism operatinginstantaneously in response to a predetermined minimum current and aplurality of branch circuit mechanismsV operable to open theirrespective branch circuits after a definite time lag in response tooverload currents less than the predetermined minimum value for whichthe main breaker mechanismgis set.

Another object of the invention is the provision of anelectric circuitbreaker having individual main and branch circuit breaker mechanisms,with the branch circuit mechanisms operating to open their respectivecircuits with a time lag in response to overload currents below apredetermined value and with the main circuit breaker mechanismoperating to open the circuit through all the branch circuit breakermechanisms substantially instantaneously upon the occurrence of anoverload above a predetermined value. 1

Other objects and features of the invention will be readily apparent tothose skilled in the art from the following specication and appendeddrawings illustrating certain preferred embodiments of the invention inwhich:-

Figure 1 is a front elevational view of the circuit breaker according tothe present invention with the front cover and the main circuit breakerhandle removed to more clearly show internal parts.

Figure `2 lis a vertical sectional view on the line II-II of Figure 1.

Figure 3 is a vertical sectional view on the line III-III of Figure 1.

Figure 4 is a partial sectional view showing the circuit breakermechanism at the top of Figure 3 in a different position.

Figure 5 is an enlarged detail view on the line V-V o'fFigure 4.

(o1. ris- 294) Figure 6 is a partial sectional view of a modified formof trip unit for the main circuit breaker mechanism,

The circuit breaker according to the present invention comprises aninsulating base I of generally cup shape, provided with a pair ofbarrier walls 3 and 4. Barrier wall 4 divides that portion of the baseenclosing the main circuit breaker mechanism from the rest of theenclosure. Barrier wall 3 provides a partial separation betweenadjacentbranchcircuitbreakermechanisms. 'I'he central .portion of thebarrier wall 3 is cut away to provide a common compartment 5 for theescape of arc gases.l That portion of wall 3 below the compartment 5 isfurther recessed to receive a fibre insulating plate 6 on which issupported a contact plate 1. 'I'he plates 6 and 1 may be rigidly securedto the base by means of a stud 8. Contact plate 'I carries contactsurfaces 9 adjacent to its corners and between contiguous contactsurfaces are .disposed openings II, permitting escape of any arc gaseswhich may be generated in the common chamber 5. The arc chambers formedby the sides of walls 3 and 4 and the adjacent .side wall of the basemay be provided with suitable fibre liners.

The switching members for the branch circuit breaker mechanisms areconstituted by floating contact members I3, carrying contact surfacesadjacent to one end cooperating with the stationery contact surfaces 9and latched at their opposite ends by current traversed bimetallicmembers I4, adjustably mounted on connectors I5 which are -rigidlymounted on ledges at the exterior of the circuit breaker enclosure bymeans of spun over portions of metallic inserts I6.

The bimetals I4 are mounted on pressed out portion I'l at the interiorends of the connectors I 5 and bridging portions I8 are .disposedbetween the pressed out portions I1 and the main portions of theconnectors and studs I9 are threaded therein for adjusting the overlapof the bimetallic members I4 with the latching ends of the contactmembers I3 and lience, for adjusting the movement of the bimetallicmembers and the value of the currents necessary to trip the mechanism.

The contact members I3 are biased against the stationary contactsurfaces 9 and the ends of bimetallic latches I4 by'means of relativelyheavy contact members I3 are provided with notches 22 which receive thefront edges of slots 23 in compression springs 2l. The front edges ofthe rectilinearly movable elements 24, guided within notches in the sidewall of the base and in the Y walls 3 and 4. Abutments 25 are pressedout of the main body of the elements 24 so as to limit the rotation ofthe contact members I3, to be hereinafter described.

Push button handles 26 are rotatably mounted upon reduced front endportions of the elements 24 and are biased against the shoulders formedat the reduced end portions by means of springs 21, bearing on shoulders28 on the push buttons.

lThe push buttons are provided with male pro jections 29 received withincorresponding female openings in a metallic cover 3|, which may besealablysecured to the base by means of spun over rivets or in any otherdesired manner. Beneath the metallic cover plate 3| is provided a iibresheet 32 having end portions 33 received within suitable notches andguides on the barrier walls 3 and 4 and the side wall of the base andserving to seal off'the ends of the branch circuit breaker enclosure. l

The bimetallic member I4 and the contact member I3 are electricallyconnected by means of a flexible lead 34 which may be brazed orotherwise secured therebetween.

To enclose the arc chambers and the common arc gas receiving chamber 5from the breaker mechanisms, fibre barrier plates 35 are provided whichhave restricted slots 36 therein receiving A the contact members I3.

Within the chamber formed by the barrier Wall A with a bre liner 43 anda bre barrier 44,

having a slot 45 closely receiving the contact member 42. The contactmember 42 has a double notch engagement with a rectilinearly movableelement 46 suitably guided for movement at right angles to the back ofthe base by guiding projections therein. a biases the contact memberY'42 against the stationary contact surface and a latching surface to behereinafter described. An operating handle 41 ispivotally mounted on ashaft 48 mounted within suitable notches 49 in the side wall of the baseand the barrier wall 4. This handle is provided with an interior camsurface cooperatying with the front face of the element 46 to move itrectilinearly, which cam surface includes a fiat portion 5I, forming astable manual OFF support for the element.

A light spring 52 biases the handle for rotation in a counter-clockwisedirection as shown and performs the function of springs 21 in thebranch' circuit breaker mechanism.

At the end of the enclosure opposite the stationary contact plate 31 ismounted a conducting support 53 as by means of a spun over portion of ametallic insert 54. To the interior end of the support 53 is welded orotherwise secured an L shaped magnetic bracket 55 to the end of which ispivotally mounted a magnetic armature latch member 56 adapted to beengaged with the end of the contact member 42 to latch it in itsoperating position. The armature 56 vis biased The compression spring41.

away from the bracket 55'by means-of a compression spring 51 and itsmovement therefrom is limited by stud 58 threaded into armature andhaving its body portion slidable within an opening in the bracket 55.Through the attachedportion of the bracket 55 is threaded a magneticscrew 59 having its inner end headed about a generally U shaped member6I which has its legs suitably guided in notches in the support 53. Ailexible lead 62 interconnects the conducting support 53 and the contactmember 42. This lead is Wound about the magnetic screw 59 and thewindings are retained in place by the U shaped member 6I.

The interior end of the magnetic screw-53 forms a pole face adapted toattract the armature 56 upon the occurrence of a predetermined overloadcurrent about the magnetic path formed by the bracket 55, the armature56 and the screw 59. The adjustment of the stud 58 will vary the overlapof the armature latch 56 with the end of the contact member 42 and willhave some eilect upon the air gap in the magnetic circuit. Adjustment ofthe screw 59 will directly vary the air gap and these two adjustments,together with the number of turns of the exible lead 62 about themagnetic screw will determine the value of the current which will tripthis main breaker mechanism.

'I'he operation of the individual branch circuit breaker mechanisms willnow be described.

The mechanism shown at thetop of Figure 3 is in the normal operating orclosed circuit position. Upon the occurrence of overload through thebimetallic member i4 it will become heated and warp toward the end ofthe base, thereby unlatching the corresponding end of the contact memberI3 which will be rotated under the bias of the spring 2I into theposition shown by the circuit breaker mechanism at the bottom of Figure3, thus moving the contact surface on the contact member away from itscooperating contact surface 9 and opening the circuit through thatbranch. This rotation of the contact member I3 will be limited by theengagement of the abutment 25 with the front edge oi' the contactmember. It is to be noticed that in this automatic opening of thecircuit, the member I3, the element 24 and the push button handle 26 areall movedl outwardly so as to place the push button handle in a positionindicating the automatic trip position oi' the breaker mechanism. Thisresult is obtained because the normal operating compression spring 2Ihas a considerably stronger bias than the handle maintaining spring 21.

To reset the parts after automatic operation, push button 26 is pressedinwardly, whereupon the back edge of the contact member I3 adjacenttoits contact surface will engage the bottom of the arc chamber and themember I3 will rotate about its pivotal engagement with the element 24to rotate the latching end back into position beneath the bimetalliclatching member I4. Release of the push button will thereafter permitthe parts to resume their normal operating position. l

If it is desired to open a branch circuit mechnism manually, the pushbutton 26 is pressed inwardly until the male projection 29 moves out ofits cooperating female opening whereupon the handle may be rotated toengage the end of this projection with the under side of the coverwhereupon the parts will assume as a stable position that shown inFigure 4. With the contacts separated in manual disengagement, to againplace the parts in closed circuit position, the push button 26 isrotated back to the position where the male projection 29 registers withthe female opening in the cover whereupon the push button will be freeto move outwardly and the parts will assume their normal closed circuitposition.

The operation of the main breaker mechanism is substantially the same asthe 4branch circuit breaker mechanism, with the exception that thehandle 41 is rotated about its pivotal shaft 48 to eect thereciprocation of the element 46. When the flat portion 5| of the camsurface engages the front surface on the element 46 the stable manualOFF position will be produced with the contact member 32 rotated todisengage its contact carrying end from the stationary contact surface4I.

This main circuit breaker is adapted to open I the circuit through allthe branch mechanisms upon the occurrence of a predetermined overloadwithout delay. This value can be set at any desired current and itsupper limit will be determined bv the rupturing capacity of the branchcircuit breaker mechanisms.

' Upon the occurrence of this predetermined value the armature 56 willbe pulled into engagement with the pole face formed by the end of themagnetic screw 59. This releases the latching end of the contact member42 and permits it to rotate in a counter-clockwise direction under thebias of the spring 41, thus interrupting the current through all thebranch circuits. This release will permit the spring 41 to overcome thespring 52 and will rotate the operating handle to indicating position.To reset breaker mechanism after an automatic trip, the handle isrotated beyond the manual OFF position. until the tip beyond the flat 5|moves the element 46 i far enough toward the base so that the latchingend of contact member 42 will be re-rotated into position beyond thearmature latch 46. Release of the handle will place the parts in themanual OFF position with the flat 5| engaging the element 46, whereuponrotation of the handle beyond the flat will again permit the parts to'assume the normal closed circuit position.

With this type of circuit breaker, it is intended that the branchcircuit breaker mechanisms will only be required to interrupt moderatesustained overloads and that short circuit currents and high overloadswill be interrupted by the main circuit breaker mechanism. With thisfunctioning considerable economy in the construction of the branchcircuit ymechanism is obtained over` the case lwhere each of the branchcircuit breaker mechanisms must be capable of interrupting short circuitcurrents.

As a practical example, the main circuit breaker mechanisms may be setto operate at 600% of the rated current of the highest rated branchcircuit mechanism. Then, for instance, if the maximum rating of a branchcircuit mechanism were 50 amperes, the branch circuit mechanisms wouldhave to be capable oi successfully interrupting 300 amperes and alloverloads above this `gvalue would always be interrupted by the nia-incircuit breaker mechanism.

The bimetallic latches I4 will always have some time lag whereas themagnetic armature latch 56 will operate without this time lag andoverloads beyond 300 amperesvwill always be interrupted by the maincircuit breaker mechanisms while the low sustained overloads will beinterrupted by the individual branch circuit breaker mechanisms withoutinterrupting the circuits through the remaining branch circuitbreakermechanisms. This permits the attainment of considerable economyin the construction of branch circuit mechanism while retaining thedesirable time lag on moderate overloads and retaining as well, theability to rupture currents of short circuit value.

vWhile the main circuit breaker tripping unit has been shown asmagnetic, it is obvious that any other type of tripping unit may be usedso `long as the time lag therein will be greater than in the trippingunits of the branch mechanisms for moderate overloadsand lesser for thehigh overload and short circuit currents, in order that the moderateoverloads will be individually interrupted by the branch circuit breakermechanisms and that high overloads and short circuits will beinterrupted by the main circuit breaker mechanism.

A slightly modified form of trip unit for the main circuit breakermechanism has been illustrated in Figure 6. Here the conducting support53 hasA been extended to receive an adjusting stud 63, bearing against amagnetic portion 64 which is welded or otherwise secured to the support53 and to the free end of which is secured a magnetlc spring latchingmember 65. The other parts remain the same as in the preferred form oftripping unit. Here the overlap of the spring latch 65 is determined byadjustment of the stud 63. This latch 65 must be sufllciently rigid towithstand the thrust of the contact member 42 but must have suiiicientresilience so as to permit bending under the attraction of the magneticfield so as to permit the latch 65 to move as an armature intoengagement with the pole face formed by the magnetic screw 59. n

While certain preferred embodiments of the invention have beenspecically disclosed, it is understood that the invention is not limitedthereto as many variations will be readily apparent to those skilled inthe art and the invention is to be given its broadest possibleinterpretation within the terms of the following claims.

What is claimed is:

l. In a multi-circuit circuit breaker adapted for main and branchcircuit protection, a plurality of branch circuit breaker mechanismshaving electrically common parts from which they are adapted to feed totheir individual circuits, saidmechanisms including means forautomatically opening the circuits therethrough upon the occurrence ofsustained moderate overloads, a main circuit breaker mechanismelectrically connected to feed to said electrically common parts andincluding means for automatically interrupty ing the circuittherethrough upon the occurrence of high overload currents, a sealableenclosure for the main and branch circuit breaker mechanisms and theconnection therebetween to prevent access thereto, and terminals forsaid circuit breaker mechanisms at the exterior of the enclosure andvaccessible for the connection of circuit wiring.

2. A unitary multi-circuit circuit breaker adapted for both main andbranch circuit protection comprising a sealable enclosure, a pluralityof individual branch circuit breaker mechanisms within said enclosurehaving means automatically operable upon the occurrence of sustainedmoderate overloads to individually open the circuits through saidmechanisms, a main circuit breaker mechanism mounted within saidenclosure and connected to feed to said branch circuit breakermechanisms, said main circuit breaker mechanism including means forinterrupting the circuit therethrough automatically operable upon theoccurrence of a relatively high overload current, and terminals for.said main and branch circuit breaker mechanisms accessible at theexterior of said sealable enclosure for the connection of circuitwiring.

3. A unitary multi-circuit circuit breaker adapted for both main andbranch circuit protection comprising a sealable enclosure, a pluralityof individualY branch circuit breaker mechanisms within said enclosureincluding means automatically operable in response to sustained moderateoverloads for individually opening the circuits through said mechanisms,a main circuit breaker mechanism mounted within said enclosure andconnected to feed to said branch circuit breaker mechanisms and havingmeans automatically operable in response to a relatively high overloadcurrent to interrupt the circuit through said main circuit breakermechanism, said last mentioned means operating with substantially notime delay upon the occurrence of a predetermined value of overloadcurrent, and terminals for said main and branch circuit breakermechanisms readily accessible at the exterior of the enclosure for theconnection of circuit wiring.

4. A unitary multi-circuit circuit breaker adapted for both main andbranch circuit protection comprising a sealable enclosure, a pluralityof branch circuit breaker mechanisms Within said enclosure having meansautomatically operable to individually open the circuits therethroughupon the occurrence of sustained moderate overloads, a main circuitbreaker mechanism mounted Within said enclosure and connected to feed tosaid branch circuit breaker mechanisms, said main circuit breakermechanism including means automatically operable vto break the circuittherethrough upon the occurrence of a relatively high overload current,said rst mentioned means respending individually to break the circuitsthrough their mechanisms upon the occurrence of sustained moderateoverloads therethrough, said last mentioned means operating before saidrst mentioned means to interrupt the circuit through the main circuitbreaker mechanism upon the occurrence of a high overload or shortcircuit current, and terminals for said main and branch circuit breakermechanisms accessible at the exterior of the enclosure for theconnection of circuit Wiring.

5. In an automatic electric circuit breaker assembly adapted for mainand branch circuit protection, a plurality of branch circuit breakermechanisms having means individually automatically operable to interruptthe current through their respective mechanisms, said means includingthermal current responsive tripping units, said mechanisms beingincapable of successfully interrupting currents of relatively high orshort circuit value, and a main circuit breaker mechanism capable ofinterrupting short circuit currents connected to -feed to said branchcircuit breaker mechanisms and including means automatically responsiveto a predetermined current value within the safe interrupting capacityof the branch circuit breaker mechanisms to interrupt the circuitthrough the main circuit breaker mechanism, said last mentioned meanscomprising a magnetic trip unit operating in response to currents abovesaid predetermined value with substantially no time delay.

6,. In a unitary multi-circuit circuit breaker adapted for main andbranch circuit protection, a

breaker mechanism mounted in one of said corn-A partments having meansautomatically operable in response to a predetermined value of currentto break the circuit therethrough, said mechanism being capable ofinterrupting currents of short circuit value, a plurality of branchcircuit breaker mechanisms in another of said compartments having meansautomatically operable in response to overload currents below saidpredetermined value for opening the circuits through the individualmechanisms, said branch circuit breaker mechanisms having a safeinterrupting capacity in excess of said predetermined value but of lessthan short circuit value, said last mentioned means being individuallyoperable with a small time delay to the current overloads to which theyare responsive, means extending between Said compartments and sealedwithin said enclosure and connecting the main circuit breaker mechanismto feed to said branch circuit breaker mechanisms, and terminals forsaid main and= branch circuit breaker mechanisms mounted at the exteriorof said enclosure and readily accessible for the connection of circuitWiring.

'7. In a unitary multi-circuit circuit breaker adapted for main andbranch circuit breaker protection, a sealable enclosure, a plurality ofelectrically common contacts Within said enclosure, a-

main circuit breakermechanism having a short circuit currentinterrupting capacity and including means automatically operable inresponse to currents above a predetermined value to interrupt thecircuit through the mechanism, said mechanism including a contactcooperating with one of said common contacts to feed theretofand aplurality of branch circuit breaker mechanisms having contactsindividually cooperating with the others of said common contacts andincluding means individually automatically operable in response tooverload currents of less than said predetermined value to individuallyinterrupt the circuits through said mechanisms at said cooperatingcontacts.

8. In a unitary multi-circuit circuit breaker adapted for main andbranch circuit breaker protection, a sealable enclosure, a contactelement within said enclosure having a plurality of contact facesthereon, a main circuit breaker mechanism having a contact cooperatingwith one of said contact faces to feed to said contact element, saidmechanism having the capacity of safely interrupting currents of shortcircuit value and including means automatically operable in response tocurrents above a predetermined minimum value to open the circuitthroughsaid mechanism at said l contact and the contact face with which itcooperates, a plurality of branch circuit breaker mechanisms havingindividual contacts cooperating with the others of said contactfaces andincluding means individually automatically operable in response tooverload currents below said predetermined minimum value to interruptthe circuits through said branch circuit breaker mechanisms at saidcontacts and contact faces, saidlast mentioned means operating with ashort time delay in response to overload currents of less thanXsaidpredetermined value, said rst mentioned means operating substantiallyinstantaneously in response to overload currents above saidpredetermined value.

9. In a unitary multi-circuit circuit breaker adapted'for main andbranch circuit protection. a cluster of stationary contact surfaces, amain circuit breaker mechanism having a contact cooperating with one ofsaid contact surfaces to feed to said cluster and including meansautomatically operable substantially instantaneously upon the occurrenceof an overload current above a predetermined value to interrupt thecircuit through said mechanism, a plurality of branch circuit breakermechanisms having individual contacts cooperating with the other of saidcontact surfaces and including means individually automatically operablewith a small time delay in response to overload currents below saidpredetermined value to interrupt the circuit through their respectivemechanisms.

f 10. In a unitary multi-circuit circuit breaker adapted for main andbranch circuit protection, a cluster of stationary contact surfaces, amain circuit breaker mechanism having a contact cooperating with one ofsaid contact surfaces to feed t0 said cluster and including meansautomatically operable substantially instantaneously upon the occurrenceof an overload current above a predetermined value to interrupt thecircuit through said mechanism, a plurality of branch circuit breakermechanisms having individual contacts cooperating with the other of saidcontact surfaces and including means individually automatically operablewith a small time delay in response to overload currents below saidpredetermined value to interrupt the circuit through their respectivemechanisms, and a sealable enclosure for said mechanisms, means,contacts and contact surfaces to prevent unauthorized access thereto,and terminals for said main and branch circuit breaker mechanismsmounted at the exterior of said enclosure and readily accessible for theconnection of circuit wiring.

11. A unitary multi-circuit circuit breaker adapted for both main andbranch circuit protection comprising a base, a main automatic electriccircuit breaker mechanism mounted on said base and including meansautomatically operable in response to overload currents above apredetermined value to break the circuit through said mechanism, aplurality of branch circuit breaker mechanisms mounted on said base andincluding means individually automatically operable in response tooverload currents below said predetermined value to interrupt thecircuits through their individual mechanisms, means connectingsaidbranch mechanisms to feed through the main mechanism, cover meanssealably attached to said base to provide a sealed enclosure for saidmechanisms and the connecting means, a main terminal for said mainmechanism supported on said base at the exterior of said enclosure, aplurality of branch terminals individually connected to the branchmechanisms and also mounted on the base at the exterior of theenclosure, and manual operating means for said mechanisms projectingthrough the cover means to the exterior of the enclosure.

l2. A unitary multi-circuit circuit breaker adapted for main and branchcircuit breaker protection comprising a base, a main circuit breakermechanism mounted on said base and including means automaticallyoperable substantially instantaneously upon the occurrence of anoverload current in excess of a predetermined value to open the circuitthrough said mechanism, a plurality of branch circuit breaker mechanismsmounted on said base and including means individually automaticallyoperable with a short time delay in response to overload currents belowsaid predetermined value to open the circuits through their individualmechanisms, cover means sealably attached to said base to provide asealed enclosure for said mechanisms and the connecting means to preventaccess thereto, terminals for said main and branch circuit breakermechanisms supported on the base at the exterior of the enclosure, andmanual operating means for said mechanisms projecting through the covermeans to the exterior of the enclosure.

13. A unitary multi-circuit circuit breaker adapted for main and branchcircuit breaker protection comprising a base, a main circuit breakermechanism mounted on said base and having a safe interrupting capacityfor currents of short circuit value, said mechanism including meansautomatically operable substantially instantaneously in response tooverload currents above a predetermined value to open the circuitthrough the mechanism, a plurality of branch circuit breaker mechanismsmounted on said base and having safe interrupting capacities in excessof said predetermined current value but of less than short circuitmagnitude, said last mentioned mechanisms including means individuallyautomatically operable with a time delay in response to overloadcurrents below said predetermined value to interrupt the circuitsthrough the individual mechanisms, means connecting said branchmechanisms to feed through the main mechanism, cover` means sealablyattached to said base to provide a sealed enclosure for said mechanismsand connecting means. terminals for said main and branch mechanismssupported on said base at the exterior of the enclosure, and manualoperating means for said mechanisms projecting through the cover meansto the exterior of the enclosure.

' JOHN G. JACKSON.

